Low-molecular-weight poly(imide-amide)s obtained by copolycondensation of 4,4′-methylenedi(phenyl isocyanate), trimellitic anhydride and benzoic acid in N-methyl-2-pyrrolidone, 2. Structural defects observed by 1H and 13C NMR

The in depth examination (by ¹H and ¹³C NMR, DSC, SEC and TGA) of the low-molecular-weight poly(imide-amide)s synthesized with the mixture [4,4′-methylenedi(phenyl isocyanate) (M) + trimellitic acid anhydride (T) + benzoic acid (B)] in N-methyl-2-pyrrolidone (NMP) at temperatures lower than 180°C allowed the identification and quantitative determinations of all the unexpected and relatively stable structures. While amide functions are readily synthesized, the formation of imide from anhydride and isocyanate functions passes through 4-amido-1,2-benzenedicarboxylic acid (Tⁱ), 1,4-di-amido-2-benzenecarboxylic acid (T″) and disubstituted urea (u). At 180°C Tⁱ completely disappears but traces of T″ and u remain; thus, the formation of imide can never reach its theoretical quantity. Traces of moisture in NMP may play the role of catalyst in the formation of imide, and reaction mechanisms are proposed.     

Low-molecular-weight poly(imide-amide)s obtained by copolycondensation of 4,4′methylenedi(phenyl isocyanate), trimellitic acid anhydride and benzoic acid in N-methyl-2-pyrrolidone, 1. The microstructure studied by 1H and 13C NMR

Low-molecular-weight poly(imide-amide)s (PIA) obtained by polycondensation at 180°C of 4,4′ -methylenedi(phenyl isocyanate), trimellitic acid anhydride and benzoic acid were studied by ¹H and ¹³C NMR. Complementary ¹H and ¹³C information was used to determine the distribution of II, IA, AA sequences and to show that the repartition of imide (I) and amide (A) groups along the chains is random. According to the composition of the monomer mixture, a slight deficiency of I is reproducibly observed. Non-reacted benzoic acid is found, and unexpected traces of urea and amic acid groups are present in the PIA chains.     

Hydroxytelechelic polybutadiene, 14. Gelation of a radically obtained hydroxytelechelic polybutadiene with 4,4′-methylenedi(phenyl isocyanate)

A new commercial radically obtained hydroxytelechelic polybutadiene (HTPB-A) was examined by ¹H NMR at 500 MHz, and a corrected interpretation of the complex proton methylene resonance of the vinyl-type primary alcohol was done. The weight-average hydroxyl functionality F?_w (OH) was determined by using critical conversions at gel points of the (HTPB-A + diisocyanate) systems, on the one hand, and swelling at equilibrium on the other. The functionality polydispersity index of HTPB-A is close to unity.     

Polyurethane ionomers: Order in 4,4′-methylenedi(phenyl isocyanate)- and hexamethylene diisocyanate-based poly(ether-urethane) cationomers

Polyurethane cationomers from poly(oxytetramethylene) of molecular weight 2000 as soft segments, 2,2′-methyliminodiethanol as chain extender, glycolic acid as quaternization agent, and 4,4′-methylenedi(phenyl isocyanate) (MDI) and hexamethylene diisocyanate (HDI) as diisocyanates are synthesized and characterized by using wide-angle X-ray diffraction, dynamic mechanical analysis, differential scanning calorimetry and tensile-elongation testing. It is found that, in the unionized and ionized cases, the hard segments exhibit a disorder and short- and long-range order, but no crystallinity. The ordered hard segments in the hard domains aggregate so tightly as to act as crosslinks, such that crystallization of soft segments occurs during elongation. Such disorder and order are also found to exist in the solutions of ethyl methyl ketone as reflected in variations of conductivity and viscosity during addition of water at 20°C. Ionization by insertion of the acid can disrupt the order in MDI and HDI systems, but can increase the cohesion between the neighbouring hard segments, the latter being predominant over the former. Dispersion is apt to disrupt the long-range order in HDI systems but has only an insignificant effect on the order in MDI systems.